Cryptocurrency Quantity Subunits

The quantity of a cryptocurrency asset in the currency's sub units.
Amount is an integer in a string format.
Floating point should be avoided to avoid precision errors. For example:

Bitcoin(BTC) has 8 decimals,

so 1 BTC will be represented as 100000000 (1 followed by 8 zeroes).

Ethereum(ETH) has 18 decimals,

so 1 ETH will be represented as 1000000000000000000 (1 followed by 18 zeroes).